摘要:

AbstractThe ascending projections of serotonin neurons of the midbrain raphe were analyzed in the rat using the autoradiographic tracing method. Axons of raphe serotonin neurons ascend in the ventral tegmental area and enter the medial forebrain bundle. A number of fibers leave the major group to ascend along the fasciculus retroflexus. Some fibers enter the habenula but the majority turn rostrally in the internal medullary lamina of the thalamus to innervate dorsal thalamus. Two additional large projections leave the medial forebrain bundle in the hypothalamus; the ansa peduncularis‐ventral amygdaloid bundle system turns laterally through the internal capsule into the striatal complex, amygdala and the external capsule to reach lateral and posterior cortex, and another system of fibers turns medially to innervate medial hypothalamus and median eminence and form a contralateral projection via the supraoptic commissures. Rostrally the major group in the medial forebrain bundle divides into several components: fibers entering the stria medullaris to terminate in thalamus; fibers entering the stria terminalis to terminate in the amygdala; fibers traversing the fornix to the hippocampus; fibers running through septum to enter the cingulum and terminate in dorsal and medial cortex and in hippocampus; fibers entering the external capsule to innervate rostral and lateral cortex; and fibers continuing forward in the medial olfactory stria to terminate in the anterior olfactory nucleus and olfactory bul

ISSN:0092-7317    

DOI:10.1002/cne.901800302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe pattern of primary auditory projections to the brain stem of young chickens was investigated using terminal degeneration methods and orthograde transport of horseradish peroxidase (HRP) or tritiated amino acid. Of particular interest was the question of whether nucleus laminaris (NL) receives primary afferents. A study of silver‐stained degeneration patterns in nucleus magnocellularis (NM) and NL at three intervals following unilateral interruption of the cochlear nerve revealed that by 48 hours after the lesion, degenerating terminals were found only in the ipsilateral nucleus angularis (NA), NM and lagenar projection areas but not in NL. Five‐ and eight‐day survival times, however, also revealed degeneration bilaterally in NL. The appearance of terminal degeneration in NL at the longer survival times is attributed to the previously‐reported severe and rapid transneuronal degeneration of neurons in NM following deafferentation and not to the presence of cochlear nerve terminals in NL. Injection of HRP or tritiated proline into the basilar papilla produced patterns of labeling similar to that seen in the 2‐day degeneration material; HRP reaction product or autoradiographic label were seen only in the ipsilateral NA and NM and in the ipsilateral projection areas of the macula lagena but not in either NL. The patterns of primary auditory projections revealed by the three methods were quite similar to each other and to that previously reported for the pigeon and confirm the conclusion that the laminar nucleus of chickens does not receive primary

ISSN:0092-7317    

DOI:10.1002/cne.901800303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

Abstractβ‐Bungarotoxin (β‐BT) was applied to chick embryos at 3‐day intervals beginning on the fourth day of incubation to investigate ultrastructurally the effects of chronically and massively applied β‐BT on various nervous tissues and muscles. On the twenty‐first day of incubation, spinal cords of β‐BT treated embryos were conspicuously decreased in size. Ventral root fibers, dorsal root fibers, white matter, and motor neurons disappeared. Although spinal ganglia and sympathetic trunk ganglia were completely absent, Auerbach's and Meissner's ganglia nerve cells in the small intestine and adrenal medullary cells were not affected. In retinas of β‐BT treated animals ganglion cells and optic nerve fibers disappeared, but photoreceptor cells, bipolar cells and horizontal cells remained intact. Furthermore, olfactory nerve cells and their unmyelinated nerve fibers ensheathed by Schwann cells were quite undamaged. Skeletal muscles degenerated, whereas cardiac muscles were unaffected. In the present study various nervous tissues of the twenty‐first day normal chick embryos were incubated with β‐BT and target cells of β‐BT were detected directly by the reaction with horseradish peroxidase labelled anti β‐BT guinea pig IgG. Motor nerve cells in the spinal cords, spinal and sympathetic ganglia nerve cells, ganglion cells and some nerve cells at the inner part of the inner nuclear layer in the retinas were positively stained, whereas Auerbach's and Meissner's ganglia nerve cells in the small intestine, adrenal medullary cells, photoreceptor cells, bipolar cells and horizontal cells in the retina and olfactory nerve cells were negative. Thus the present study shows that β‐BT has extensive destructive effects on various nerve cells which were revealed to be target neurons of β‐BT by immunocytochemistry. Those nerve cells, affected by β‐BT and positively stained with immunocytochemical reaction were supposed to have different characteristics from unaffected cells. One of the differences between these affected cells and unaffected cells may be whether there exist binding sites for β‐BT on the plasma membrane or not. The possibility of the use of β‐BT to characterize various nervo

ISSN:0092-7317    

DOI:10.1002/cne.901800304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe possible presence of a blood‐myenteric plexus barrier similar to the blood‐ nerve and blood‐brain barriers was investigated. The myenteric plexus was found to be an enclosed tubular structure incompletely surrounded by a sheath of supporting cell processes. Capillaries do not enter the plexus. The capillaries which supply the myenteric layer differ in structure from capillaries of other layers of the gut and are non‐fenestrated. Tracers, Evans blue labeled albumin or horseradish peroxidase, readily leak out of fenestrated capillaries, but do not readily escape from myenteric capillaries. These capillaries have impermeable junctions that prevent the passage of tracer between endothelial cells. A slow leakage of macromolecules is probably accounted for by transport through endothelial cells within plasmalemmal vesicles. A backup system of phagocytic cells removes this material and prevents the tracers leaking from the vasculature from reaching detectable concentrations in the extracellular space. Neither tracer was ever found in the myenteric plexus. Therefore, there is a blood‐myenteric plexus barrier to macromolecules that resembles the bloodthymic barrier and may be functionally analogous to the blood‐br

ISSN:0092-7317    

DOI:10.1002/cne.901800305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractA method was devised for morphological localization of the area centralis, and the timecourse of its formation as a structural entity was established. Postnatal differentiation of the retina proceeds as follows: the irregularly laminated ganglion cell layer of the newborn becomes unilaminar everywhere but in the presumptive area centralis, a difference which is first discernible at five to six days of age; the outer nuclear layer is always of the same thickness in the area centralis, while in the periphery the layer thins with time; the outer nuclear layer is always thinner in the area centralis than in the periphery; inner nuclear layer thickness is invariant early in postnatal life, but in the adult it is thicker in the area centralis than in the near temporal periphery; plexiform layers from by two weeks of age and reach adult thickness thereafter.Retinal ganglion cells were measured and the percent distributions of three ganglion cell size classes (6–10 μm; 11–20 μm; 21–35 μm) were determined for the area centralis and near temporal periphery. Mean ganglion cell size is constant in center and periphery through five weeks of age, is adultlike in the periphery soon thereafter and in the center sometime after eight weeks of age. The percent distribution of ganglion cells by size class in center and periphery is not adultlike even at eight weeks of age. The implications of these observations and others are discussed relative to postnatal growth of the eye and placement of the area centralis in the retinal field and optic axis. The involvement of retinal cell proliferation, cell growth, ganglion cell dendrite formation and cell shape changes in the expansion of the retina are also d

ISSN:0092-7317    

DOI:10.1002/cne.901800306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of proliferative disorders on the time and sequence of neuron origin in the optic tectum were studied in chick embryos in which “overgrowth” had been experimentally induced. Sixteen normal and fourteen abnormal embryos ranging in age from four through ten days of incubation were each given a single dose of thymidine[3H]. Comparisons were then made between 16‐day normal and abnormal chick embryos with respect to the distribution of unlabeled and labeled neurons in the dorsolateral regions of the optic tectum midway between its rostral and caudal boundaries. In the normal and abnormal tecta layers I‐IV were generated on days 3–6. Differences occurred in the generation of the remaining layers. In the normal embryos layers V‐VII arose on days 5–8 and layers VIII‐XV on days 4–7; in the abnormal embryos layers V‐VII originated on days 6–8 and layers VIII‐XV on days 5–8. In addition to the delay in onset of neuron origin, the abnormal tectum also showed distorted lamination, particularly in layers VIII‐XV which constitute the superficial regions of the stratum griseum and fibrosum superficiale. Despite the defect in time and sequence of neuron origin, the rostroventrolateral to caudodorsomedial gradient of maturity characteristic of the normal tecta was not dist

ISSN:0092-7317    

DOI:10.1002/cne.901800307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe catecholamine (CA) innervation of the posterior basal forebrain, the amygdala, suprarhinal cortex and entorhinal cortex, was studied in the rat using biochemical assay and fluorescence histochemistry. The assay studies demonstrate a moderate norepinephrine (NE) content in the amygdala and entorhinal cortex with a lower value for the suprarhinal cortex. Following destruction of the locus coeruleus, the decrease in NE content of these basal forebrain structures indicates that their principal NE innervation is from locus coeruleus. An additional small NE input arises from the medullary NE neuron groups. Ablation of dopamine (DA) cell groups (substantia nigra‐ventral tegmental area, SN‐VTA) indicates that the DA input to the amygdala arises from the lateral VTA and medial half of the SN.Fluorescence histochemical studies using the glyoxylic acid‐Vibratome technique demonstrate the presence of four distinct types of CA neuron terminal plexus in the posterior basal forebrain. These include two different DA fiber types arising in SN‐VTA, small NE fibers with small varicosities arising in locus coeruleus and NE fibers with larger varicosities arising in other brainstem NE cell groups. The large NE fibers appear to enter the amygdala via the ansa peduncularis‐ventral amygdaloid bundle to innervate the central and basolateral nucleus and the anterior amygdaloid area. The locus coeruleus NE fibers appear to enter the posterior basal forebrain via both the stria terminalis and ansa peduncularis‐ventral amygdaloid bundle system to form a moderately dense innervation of the central and basolateral nuclei of the amygdala and a less dense innervation of the other areas. The DA neuron axons are concentrated in the central and basal nuclei and intercalated cell groups. Other areas receive a more diffuse DA input, with the exception of the moderately dense innervation of the suprarhinal cortex and DA “islands” in the ventral‐anterior entorhinal cortex. The DA input to the posterior basal forebrain is complex and heterogeneous and the axonal morphology differs greatly among the terminal fields within the amygdala and adjace

ISSN:0092-7317    

DOI:10.1002/cne.901800308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe catecholamine innervation of the olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex was studied in the rat using biochemical analysis and fluorescence histochemistry. Biochemical studies demonstrate a moderate norepinephrine (NE) content in all olfactory structures, a high dopamine (DA) content in the olfactory tubercle and a low DA content in the olfactory bulb, anterior olfactory nucleus and piriform cortex. Following locus coeruleus lesions NE content decreases 71% in the olfactory bulb, 82% in the anterior olfactory nucleus, 62% in olfactory tubercle and 77% in piriform cortex. Brainstem transection caudal to locus coeruleus results in a decrease of NE in the olfactory tubercle of 35% without significant changes in other olfactory structures. Following lesions of the medial substantia nigra (SN) extending into the ventral tegmental area (VTA), there is a decrease of DA content (92%) in the olfactory tubercle. VTA lesions produce smaller decreases in olfactory tubercle DA content (79%). The area included in the SN and VTA lesions overlaps, suggesting that both the VTA and SN provide DA in nervation to the olfactory tubercle. VTA lesions also produce decreases in anterior olfactory nucleus DA content (73%) whereas medial SN lesions produce decreases in piriform cortex DA content (44%). Fluorescence histochemical studies using the glyoxylic acid‐Vibratome technique demonstrate the presence of several catecholamine (CA) fiber types in the olfactory system, including large NE fibers in the olfactory tubercle which probably originate in the caudal brainstem, fine NE fibers innervating all four olfactory structures arising from the locus coeruleus, and fine DA fibers from SN‐VTA. These innervate the olfactory tubercle, the anterior olfactory nucleus, piriform cortex and olfactory bulb. The DA innervation is very dense in all layers of the olfactory tubercle, with a variable innervation of the islands of Calleja. The DA fibers enter the olfactory tubercle as fascicles from the medial forebrain bundle. Both NE and DA fibers enter the anterior olfactory nuclei to form a sparse to moderately dense innervation with some continuing in the medial olfactory tract into the olfactory bulb. A moderately dense NE innervation is evident in the inner plexiform and granule cell layer of the accessory olfactory bulb and the granule cell layer of the olfactory bulb. Additional NE fibers are distributed sparsely throughout the remaining components of the olfactory bulb, some entering the glomeruli. There is a very sparse extrinsic DA innervation to the plexiform layer of the olfactory bulb and an intrinsic DA innervation from juxtaglomerular ce

ISSN:0092-7317    

DOI:10.1002/cne.901800309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractIn this study the location of dopamine (DA) neuron perikarya in the rostral mesencephalon of the rat was determined using the glyoxylic acid fluorescence histochemical technique. Subsequently the topography of the projection of these mesencephalic neurons on the basal forebrain and striatum was analyzed using the anterograde transport‐autoradiographic tracing method and the retrograde transport‐horseradish peroxidase (HRP) technique. The results of these anatomical studies were correlated with the biochemical and histochemical studies presented in previous reports (Moore, 1978; Fallon and Moore, 1978; Fallon et al., 1978) to provide the following conclusions. The topography of the DA neuron projection on the basal forebrain and neostriatum is organized in three planes, dorsal‐ventral, medial‐lateral and anterior‐posterior. DA cells are found almost exclusively in the substantia nigra (SN) and ventral tegmental area (VTA). Ventral cells of the SN and VTA project to the dorsal structures of the basal forebrain such as the septum, nucleus accumbens and neostriatum. The latter includes some DA cells located ventrally in the pars reticulata of the SN. Dorsal cells project to ventral structures. The medial‐lateral topography is organized such that the medial sectors of the SN‐VTA area project to the medial parts of nuclei in the basal forebrain and neostriatum whereas lateral sectors of the SN‐VTA area project to the lateral parts of nuclei in the basal forebrain and neostriatum. An anterior‐posterior topography also is evident such that anterior parts of the SN‐VTA project anteriorly whereas the posterior SN‐VTA projects more posteriorly in these areas. These observations are consistent with the view that the DA neurons of the SN‐VTA complex form a single nuclear group with a highly topographically organized projection innervating not only deep nuclei of the telencephalon but allocort

ISSN:0092-7317    

DOI:10.1002/cne.901800310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe inner one‐third of the dendritic region of the dentate gyrus granule cells in adult rats receives projections primarily from the commissural fibers of the contralateral hippocampus and the associational fibers of the ipsilateral hippocampus. At two to four days following the complete removal of the contralateral hippocampus, approximately 25% of the terminals in the inner molecular layer are observed degenerating. This provides an excellent model system to investigate possible terminal proliferation induced by deafferentation since (1) the experimental lesion is easily reproducible, (2) no retrograde reactions occur in the granule cells as a direct result of the lesion, (3) no shrinkage is detected in this region following commissural deafferentation, (4) the same dendritic region can be relocated precisely in each animal, and (5) the synaptic counts are highly consistent between animals.Results from this study and from previous investigations demonstrate that the commissural projection is contained within a 0–80 μ zone directly above the granule cell layer. Complete photomontages of this zone were taken, but only the 40–80 μ zone was quantified for neuronal and glial changes in three normal, five 2‐ to 4‐day, and five 50‐ to 75‐day postlesion animals. The average synaptic count dropped to 64% of control values by 2 to 4 days, but returned to 97% by 50‐ to 75 days postlesion. The number of terminals showing multiple synaptic contacts increased slightly in the long‐term animals. Measurements of average terminal area showed no change between the short‐ and long‐term survival groups. These results indicate that this dendritic region is reinnervated following partial deafferentation and that the reinnervation is due primarily to the formation of new terminals rather than the expansion of

ISSN:0092-7317    

DOI:10.1002/cne.901800311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY